Many semiconductor devices are formed by processes performed on a substrate such as a wafer (e.g., silicon wafer). As an example, many semiconductor devices are formed by growing successive metal oxide layers using a CVD (chemical vapor deposition) system, such as a MOCVD (metal organic CVD) system. In such a process, the wafers are exposed to a gas or combination of gases which flow over the surface of the wafer while the wafer is maintained at an elevated temperature. Prior to the flow of gas(es), the chamber in which the wafer is located is evacuated of air. During the deposition process, the chamber may be at elevated pressure. The seals in the system are paramount to having accurate processing conditions.